To meet daily increasing application requirements of users, wireless local area network standards have been evolving rapidly in the past years, and have been developing from the United States Institute of Electrical and Electronics Engineers (Institute of Electrical and Electronics Engineers, IEEE for short hereinafter) 802.11a/b/g to IEEE 802.11n and then to IEEE 802.11ac. Bandwidths that are supported in the wireless local area network standards also keep increasing, where a bandwidth of 20 MHz is supported in IEEE 802.11a/b/g, bandwidths of 20 MHz and 40 MHz are supported in IEEE 802.11n, and then bandwidths of 20 MHz, 40 MHz, 80 MHz, and 160 MHz are supported in IEEE 802.11ac. A high efficiency wireless local area network (High Efficiency WLAN, HEW for short hereinafter) system that is being researched even supports a larger bandwidth.
In the prior art, an example in which IEEE 802.11n supports 40 MHz is used. To increase a throughput of a wireless local area network system, a physical layer protocol data unit (Physical layer Protocol Data Unit, PPDU for short hereinafter) transmitted between a wireless access point (Access Point, AP for short hereinafter) and user equipment includes two parts: a preamble and data. In the part of the preamble, a legacy short training field (Legacy Short Training Field, L-STF for short hereinafter), a legacy long training field (Legacy Long Training Field, L-LTF for short hereinafter), legacy signaling (Legacy Signaling, L-SIG for short hereinafter), and high throughput signaling (High Throughput Signaling, HT-SIG for short hereinafter) are transmitted on 2 pieces of 20 MHz (that is, transmitted on 2*64=128 subcarriers), and a high throughput short training field (High Throughput Short Training Field, HT-STF for short hereinafter), a high throughput long training field (High Throughput Long Training Field, HT-LTF for short hereinafter), and a high throughput data (High Throughput Data, HT-Data for short hereinafter) part are transmitted on a channel of 40 MHz (that is, transmitted on 128 subcarriers), so as to make a throughput of a system supporting 40 MHz in IEEE 802.11n larger than a throughput of a system supporting 20 MHz in IEEE 802.11n or IEEE802.11a.
However, in the prior art, a change (increase or decrease) in a throughput of a system is limited.